content/common/gpu/media/h264_dpb.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4 //
   5 // This file contains an implementation of an H.264 Decoded Picture Buffer
   6 // used in H264 decoders.
   7
   8 #ifndef CONTENT_COMMON_GPU_MEDIA_H264_DPB_H_
   9 #define CONTENT_COMMON_GPU_MEDIA_H264_DPB_H_
  10
  11 #include <vector>
  12
  13 #include "base/basictypes.h"
  14 #include "base/memory/scoped_vector.h"
  15 #include "media/filters/h264_parser.h"
  16
  17 namespace content {
  18
  19 // A picture (a frame or a field) in the H.264 spec sense.
  20 // See spec at http://www.itu.int/rec/T-REC-H.264
  21 struct H264Picture {
  22   enum Field {
  23     FIELD_NONE,
  24     FIELD_TOP,
  25     FIELD_BOTTOM,
  26   };
  27
  28   // Values calculated per H.264 specification or taken from slice header.
  29   // See spec for more details on each (some names have been converted from
  30   // CamelCase in spec to Chromium-style names).
  31   int top_field_order_cnt;
  32   int bottom_field_order_cnt;
  33   int pic_order_cnt;
  34   int pic_order_cnt_msb;
  35   int pic_order_cnt_lsb;
  36
  37   int pic_num;
  38   int long_term_pic_num;
  39   int frame_num;  // from slice header
  40   int frame_num_offset;
  41   int frame_num_wrap;
  42   int long_term_frame_idx;
  43
  44   media::H264SliceHeader::Type type;
  45   bool idr;  // IDR picture?
  46   bool ref;  // reference picture?
  47   bool long_term;  // long term reference picture?
  48   bool outputted;
  49   // Does memory management op 5 needs to be executed after this
  50   // picture has finished decoding?
  51   bool mem_mgmt_5;
  52
  53   Field field;
  54
  55   // Values from slice_hdr to be used during reference marking and
  56   // memory management after finishing this picture.
  57   bool long_term_reference_flag;
  58   bool adaptive_ref_pic_marking_mode_flag;
  59   media::H264DecRefPicMarking
  60       ref_pic_marking[media::H264SliceHeader::kRefListSize];
  61
  62   typedef std::vector<H264Picture*> PtrVector;
  63 };
  64
  65 // DPB - Decoded Picture Buffer.
  66 // Stores decoded pictures that will be used for future display
  67 // and/or reference.
  68 class H264DPB {
  69  public:
  70   H264DPB();
  71   ~H264DPB();
  72
  73   void set_max_num_pics(size_t max_num_pics);
  74   size_t max_num_pics() { return max_num_pics_; }
  75
  76   // Remove unused (not reference and already outputted) pictures from DPB
  77   // and free it.
  78   void DeleteUnused();
  79
  80   // Remove a picture by its pic_order_cnt and free it.
  81   void DeleteByPOC(int poc);
  82
  83   // Clear DPB.
  84   void Clear();
  85
  86   // Store picture in DPB. DPB takes ownership of its resources.
  87   void StorePic(H264Picture* pic);
  88
  89   // Return the number of reference pictures in DPB.
  90   int CountRefPics();
  91
  92   // Mark all pictures in DPB as unused for reference.
  93   void MarkAllUnusedForRef();
  94
  95   // Return a short-term reference picture by its pic_num.
  96   H264Picture* GetShortRefPicByPicNum(int pic_num);
  97
  98   // Return a long-term reference picture by its long_term_pic_num.
  99   H264Picture* GetLongRefPicByLongTermPicNum(int pic_num);
 100
 101   // Return the short reference picture with lowest frame_num. Used for sliding
 102   // window memory management.
 103   H264Picture* GetLowestFrameNumWrapShortRefPic();
 104
 105   // Append all pictures that have not been outputted yet to the passed |out|
 106   // vector, sorted by lowest pic_order_cnt (in output order).
 107   void GetNotOutputtedPicsAppending(H264Picture::PtrVector& out);
 108
 109   // Append all short term reference pictures to the passed |out| vector.
 110   void GetShortTermRefPicsAppending(H264Picture::PtrVector& out);
 111
 112   // Append all long term reference pictures to the passed |out| vector.
 113   void GetLongTermRefPicsAppending(H264Picture::PtrVector& out);
 114
 115   // Iterators for direct access to DPB contents.
 116   // Will be invalidated after any of Remove* calls.
 117   typedef ScopedVector<H264Picture> Pictures;
 118   Pictures::iterator begin() { return pics_.begin(); }
 119   Pictures::iterator end() { return pics_.end(); }
 120   Pictures::reverse_iterator rbegin() { return pics_.rbegin(); }
 121   Pictures::reverse_iterator rend() { return pics_.rend(); }
 122
 123   size_t size() const { return pics_.size(); }
 124   bool IsFull() const { return pics_.size() == max_num_pics_; }
 125
 126   // Per H264 spec, increase to 32 if interlaced video is supported.
 127   enum { kDPBMaxSize = 16, };
 128
 129  private:
 130   Pictures pics_;
 131   size_t max_num_pics_;
 132
 133   DISALLOW_COPY_AND_ASSIGN(H264DPB);
 134 };
 135
 136 }  // namespace content
 137
 138 #endif  // CONTENT_COMMON_GPU_MEDIA_H264_DPB_H_